The 24-year-old Austrian scraped into the end-of-season tournament in London 12 months ago and appeared to get caught up in the occasion as he only managed to win one game and crashed out at the group stage.
But Thiem returns to the O2 Arena for the second time feeling a lot more confident about his chances following a good year which saw him reach the semi-finals of the French Open in June.
He said: "There was a lot of pressure on me last year. It was something completely new for me.
"I was nervous, it’s very different this year. I qualified as the fourth player so I’m not the last player – it feels better. I think I can enjoy it more this year. I’m not really tired. Last year I was for sure.
"I had some good practice. I’m feeling very fresh."
Thiem will go up against Grigor Dimitrov in his opening group match on Monday and he is expecting a tough test ahead of further matches against world number one Rafael Nadal and David Goffin.
Thiem added: "He had a great season. You have to have a great one to qualify here. He deserves it 100% to be here. I’m looking forward to opening the tournament here against him. It will be a fun one on Monday."